STRUCTURE OF THE SPLEEN. 733 



blood glands; and, lastly, from their influence on the blood, being en- 

 tirely exerted on that fluid within its vessels, they have been termed 

 vascular glands. By some, the closed sacs already described (p. 604), 

 as being found in the mucous membrane of the alimentary canal, if 

 not classified as mere dependencies of the lymphatic system, are ar- 

 ranged with the ductless glands. 



The organic processes proper to these ductless glands partake both 

 of the characters of nutrition, and secretion. Their substance is nour- 

 ished like that of a muscle, but each, acting like a gland, separates 

 from the blood something very special. On the other hand, although, 

 like a muscle, and unlike a gland, they do not yield up their products 

 directly by a duct, yet they doubtless impart to the blood, not merely 

 the effete materials from their waste, but the substances formed by 

 their special elaborative or assimilating power, substances essential 

 to the constitution of the blood itself. They might be termed nutri- 

 tive or assimilative glands. 



The Spleen. This organ is a soft, dark, bluish body, attached to 

 the cardiac end of the stomach; it is placed beneath the diaphragm, 

 and is nearly or quite covered by the lower ribs. Its shape is a flat- 

 tened oval, convex and smooth on its left surface, and concave on the 

 right surface, which is applied to the great cul-de-sac of the stomach. 

 Along this surface is a vertical fissure, named the hilus, sometimes 

 notched in front, at which the bloodvessels, lymphatics, and nerves 

 pass in or out. By these last-named parts, by a peritoneal duplica- 

 ture, named the gastro- splenic omentum, and by a reflection of the 

 peritoneum from the spleen on to the diaphragm, named the suspen- 

 sory ligament, this organ is held in its place. 



The size and weight of the spleen vary more than those of any other 

 solid organ in the body, not only in different persons, but at different 

 times in the same individual. This is chiefly owing to changes in the 

 quantity of blood it contains. It usually measures about 5 inches in 

 length, 3J from front to back, and 1 J from side to side ; its average 

 weight is about 6 ounces, but it may vary from 4 to 10 ounces. Up 

 to the age of forty, its proportionate weight to that of the body, is as 

 1 to 350; after that age, the ratio diminishes gradually to 1 to 700. 

 In ague and other fevers, the spleen becomes enlarged by increase of 

 substance, as well as by distension with blood, sometimes weighing 

 20 Ibs. In certain diseased conditions of this organ, it has weighed 

 40 Ibs. ; on the other hand, it has been reduced to J of an ounce in 

 weight. Its specific gravity is about 1060. 



Within the peritoneal serous covering, the spleen has a proper, 

 strong, fibro-elastic coat, which is prolonged, at the hilus, into the 

 interior of the organ, forming elastic sheaths around the bloodvessels, 

 lymphatics, and nerves. Crossing in every direction between these 

 sheaths and the inner surface of the elastic coat, are numerous slender 

 elastic bands, named trabeculce (trabs, a beam). In the spaces, or lo- 

 culi, formed between these trabeculae, outside the vessels, is contained 

 the so-called splenic pulp. This is a soft, bluish-red or brownish 

 mass, which may be pressed out from the intertrabecular spaces, and 

 which becomes of a brighter red when exposed to the air. 



